Gates

A binary and ternary logic simulation library in C++

Background

I've always had a passing interest in ternary logic, but never the drive to do so since there I didn't have a practical reason for it.

I still don't.

But upon learning the binary and ternary combinatorial circuits work in similar ways I was curious.

And curiousity is a good enough reason to break out the C++ compiler, build some obtuse-looking templates, and start building!

The library

It's simple enough, with all the logic held in gates/gate.h. TBH, as much work went into the test suite as went into the logic. The meant I was able to improve the library, utilising C++ features like operator overloads, implicit conversions, etc, and re-test after each build. Not so much a time saver, but a great safety net.

You can create gates with:

using namespace Gate;

	TernaryGateNand2 nand(PinTernary::TrueState, PinTernary::UndeterminedState);
	std::cout << nand.getResult().asString();

Implicit conversions exist for the basic gates so the line:

	std::cout << nand.getResult().asString();

can be written:

	std::cout << nand;

More complex gates and circuits can be generated by chaining, as you'd expected. One example can be found in the Xor2 code:

		Xor2(const pintype &a, const pintype &b) {
			Nand2<pintype> nand1(a, b);
			Nand2<pintype> nand2(a, nand1);
			Nand2<pintype> nand3(nand1, b);

			m_Result = Nand2<pintype>(nand2, nand3);
		}

and full adder:

		FullAdder(const pintype &a, const pintype &b, const pintype &carry) {
			HalfAdder<pintype> ha1(a, b);
			HalfAdder<pintype> ha2(ha1.getSum(), carry);
			m_Result = ha2;			

			Or2<pintype> or(ha1.getCarry(), ha2.getCarry());
			m_Carry = or;			
		}

In addition to the test suite, it also features methods to display truth tables.

Internals

There are two main parts: pins and gates.

Pins indicate the number of states that an interconnect has. 2 for binary, 3 for ternary.

Gates have a number of pin inputs, and (potentially) a different number of pin outputs.